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SUNRPC: fix races on PipeFS MOUNT notifications 

Below are races, when RPC client can be created without PiepFS dentries

CPU#0					CPU#1
-----------------------------		-----------------------------
rpc_new_client				rpc_fill_super
rpc_setup_pipedir
mutex_lock(&sn->pipefs_sb_lock)
rpc_get_sb_net == NULL
(no per-net PipeFS superblock)
					sn->pipefs_sb = sb;
					notifier_call_chain(MOUNT)
					(client is not in the list)
rpc_register_client
(client without pipes dentries)

To fix this patch:
1) makes PipeFS mount notification call with pipefs_sb_lock being held.
2) releases pipefs_sb_lock on new SUNRPC client creation only after
registration.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Stanislav Kinsbursky 2013-06-24 11:52:38 +04:00 committed by Trond Myklebust
parent 52fcac988a
commit 384816051c
2 changed files with 18 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
net/sunrpc/clnt.c
View File

@ -157,20 +157,15 @@ static struct dentry *rpc_setup_pipedir_sb(struct super_block *sb,
}
static int
rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name)
rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name,
struct super_block *pipefs_sb)
{
struct net *net = rpc_net_ns(clnt);
struct super_block *pipefs_sb;
struct dentry *dentry;
clnt->cl_dentry = NULL;
if (dir_name == NULL)
return 0;
pipefs_sb = rpc_get_sb_net(net);
if (!pipefs_sb)
return 0;
dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt, dir_name);
rpc_put_sb_net(net);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
clnt->cl_dentry = dentry;
@ -296,6 +291,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
struct rpc_clnt *clnt = NULL;
struct rpc_auth *auth;
int err;
struct super_block *pipefs_sb;
/* sanity check the name before trying to print it */
dprintk("RPC: creating %s client for %s (xprt %p)\n",
@ -354,9 +350,12 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
atomic_set(&clnt->cl_count, 1);
err = rpc_setup_pipedir(clnt, program->pipe_dir_name);
if (err < 0)
goto out_no_path;
pipefs_sb = rpc_get_sb_net(rpc_net_ns(clnt));
if (pipefs_sb) {
err = rpc_setup_pipedir(clnt, program->pipe_dir_name, pipefs_sb);
if (err)
goto out_no_path;
}
auth = rpcauth_create(args->authflavor, clnt);
if (IS_ERR(auth)) {
@ -369,11 +368,16 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
/* save the nodename */
rpc_clnt_set_nodename(clnt, utsname()->nodename);
rpc_register_client(clnt);
if (pipefs_sb)
rpc_put_sb_net(rpc_net_ns(clnt));
return clnt;
out_no_auth:
rpc_clnt_remove_pipedir(clnt);
if (pipefs_sb)
__rpc_clnt_remove_pipedir(clnt);
out_no_path:
if (pipefs_sb)
rpc_put_sb_net(rpc_net_ns(clnt));
kfree(clnt->cl_principal);
out_no_principal:
rpc_free_iostats(clnt->cl_metrics);

3
net/sunrpc/rpc_pipe.c
View File

@ -1127,6 +1127,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
return -ENOMEM;
dprintk("RPC: sending pipefs MOUNT notification for net %p%s\n",
net, NET_NAME(net));
mutex_lock(&sn->pipefs_sb_lock);
sn->pipefs_sb = sb;
err = blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
RPC_PIPEFS_MOUNT,
@ -1134,6 +1135,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
if (err)
goto err_depopulate;
sb->s_fs_info = get_net(net);
mutex_unlock(&sn->pipefs_sb_lock);
return 0;
err_depopulate:
@ -1142,6 +1144,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
sb);
sn->pipefs_sb = NULL;
__rpc_depopulate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF);
mutex_unlock(&sn->pipefs_sb_lock);
return err;
}